BigDog is described by its developers Boston Dynamics as “the most advanced quadruped robot on Earth”. The company have released a new video of the robot negotiating steep slopes, crossing rocky ground and dealing with the sharp kick. View the impressive clip here (28MB Windows media file).

“Internal force sensors detect the ground variations and compensate for them,” says company president and project manager Marc Raibert. “And BigDog's active balance allows it to maintain stability when we disturb it.'

This active balance is maintained by four legs, each with three joints powered by actuators and a fourth 'springy' joint. All the joints are controlled by an onboard PC processor.Robotic pack mule

The project is sponsored by the US Defense Advanced Research Projects Agency (DARPA), who want the robotic pack mule to assist soldiers in terrain too tough for vehicles. Ground-based soldiers often need to carry 40 kilograms of equipment.

Raibert says the latest version of BigDog can handle slopes of 35° – a steeper gradient than one in two. The hydraulics are driven by a two-stroke single-cylinder petrol engine, and it can carry over 40 kg, about 30% of its bodyweight. The robot can follow a simple path on its own, or can be remotely controlled."